define([
        '../Core/freezeObject'
    ], function(
        freezeObject) {
    'use strict';

    /**
     * Represents the position relative to the terrain.
     *
     * @exports HeightReference
     */
    var HeightReference = {
        /**
         * The position is absolute.
         * @type {Number}
         * @constant
         */
        NONE : 0,

        /**
         * The position is clamped to the terrain.
         * @type {Number}
         * @constant
         */
        CLAMP_TO_GROUND : 1,

        /**
         * The position height is the height above the terrain.
         * @type {Number}
         * @constant
         */
        RELATIVE_TO_GROUND : 2
    };

    return freezeObject(HeightReference);
});
